The use of snow throwers (or snowblowers) by both commercial and residential operators is common for those located in snowy winter climates. These snow throwers may be walk-behind units or may be propelled by other machinery (e.g., all-terrain vehicles, tractors, etc.). Typically, snow throwers are divided into two categories: single-stage snow throwers and two-stage snow throwers. Single-stage snow throwers generally incorporate an impeller assembly that is driven by an internal combustion engine (or similar prime mover) to perform the functions of propelling the snow thrower forward, lifting snow from the surface to be cleared, and ejecting the snow out of a discharge chute. Alternatively, a two-stage snow thrower comprises a separate auger assembly and impeller assembly. Both the auger assembly and impeller assembly are driven by an internal combustion engine (or similar prime mover). The auger assembly rotates near the surface to be cleared in order to lift and direct snow and debris to the impeller assembly, which rotates along an axis perpendicular to the axis of rotation of the auger assembly. The impeller assembly then acts to eject snow out of a discharge chute.
In single-stage snow throwers, the impeller assembly is generally formed of a flexible material which contacts the surface to be cleared as it is directed along a path by the user. Due to this direct contact with the surface, single-stage snow throwers typically clear the entire surface of snow quite well. However, because the impeller assembly performs the tasks of propelling the snow thrower, lifting the snow, and ejecting the snow from the discharge chute, there are limitations to the size, shape, and material of the impeller assembly. These limitations reduce the effectiveness of the impeller assembly of a single-stage snow thrower in deep, icy, and/or heavy snow conditions.
On the other hand, two-stage snow throwers are generally more adept at clearing deep and/or heavy snow than their single-stage counterparts. This is because the auger assembly of two-stage snow throwers is typically formed of a rigid material (e.g., metal) that both separates and lifts the snow to be cleared and delivers it to the impeller assembly for ejection from the discharge chute. However, as the auger assembly is formed as a rigid, non-continuous component, the auger assembly is generally positioned within an auger housing so as to be a certain distance above the surface to be cleared. While in some ways it is advantageous for the rigid auger assembly to not contact the surface to be cleared, there is also the potential disadvantage of some snow being left behind and/or compacted as the snow thrower passes. Additionally, two-stage snow throwers are also generally much heavier and more costly than single-stage snow throwers.
Referring to FIG. 1, a conventional assembly for a single-stage snow thrower is shown. An output shaft is connected to an impeller 6, which is supported within a forward portion of the housing by a drive connection. The rear portion of the housing is supported by wheels 7. A handle 8 extends rearwardly of the housing. A control bar 9 is pivotally connected to the upper portion of handle 8 and is capable of being actuated by an operator. The control bar 9 is connected by a cable 10 to the drive connection between the engine's output drive shaft and the impeller 6. During operation of the engine, the operator selectively actuates the control bar 9 to complete the drive connection between the engine and the impeller whereby snow is moved by the impeller 6 and is discharged from the housing through a discharge port provided in the housing above the central portion of impeller 6. An adjustable discharge chute 12 is joined to the port to direct snow thrown by impeller 6. A control rod 15 extends from one of its ends, positioned adjacent to handle 8, to a worm gear (not shown) which is joined to the rod's opposite end. The worm gear is positioned in operative relationship with chute 12 to cause the chute to rotate about a vertical axis in response to actuation of control rod 15 to thereby control the direction of snow discharged from the snow thrower. The distance the snow is thrown is established by the position of a deflector 16 which is pivotally connected about a horizontal axis to the top of chute 12.
Referring to FIG. 2, a schematic side view of a conventional impeller and impeller housing assembly for a single-stage snow thrower is shown. The assembly comprises an impeller 102 coupled to a driven shaft (not shown) which rotates along a path 104 within impeller housing 106 having a mouth 107. Impeller 102 operates to propel collected snow out of a discharge chute (not shown) of the snow thrower via flexible paddles formed of any suitable flexible material, e.g. rubber. Rotational path 104 has a diameter of about 10 inches, while housing 106 is shown as having a height of 12 inches and a depth of 12 inches. Impeller 102 is driven to rotate at a speed of about 1100 RPM. As impeller 102 rotates about path 104 in a direction indicated by arrow 108, the flexible paddles of impeller 102 contact the surface to be cleared of snow to not only lift and propel the snow out of a discharge chute, but also to propel the snow thrower in a forward direction of travel as indicated by arrow 110. However, as discussed above, icy or heavy snow is not readily broken down by impeller 102 alone, which may cause substantial clogging within the impeller housing and/or discharge chute.